Modular tapered hollow reamer for medical applications

ABSTRACT

An easy-to-assemble reamer for medical applications includes a shaft portion, a disposable tapered hollow reamer sleeve and a modular pilot. The shaft portion has a proximal end for attachment to a drill, a central cone element with one or more slots and a distal threaded end. The tapered hollow reamer sleeve has integrally attached one or more torque transmitting tabs at the larger end and a collet taper at the smaller end and slides over the shaft distal end engaging tabs with the slots. The modular pilot has a threaded central aperture engaging shaft thread and a collet taper mating with the collet taper of the reamer sleeve substantially coinciding their centerlines. The disposable hollow cutter sleeve has a plurality of cutting elements and apertures that discharge bone and bone cement debris into the space between the reamer and the shaft. With this construction, the reamer transmits reliable, wobble free, reaming torque in a highly efficient manner.

This is a Continuation-In-Part of application Ser. No. 11/704,754, FiledFeb. 9, 2007 for “Hollow Reamer For Medical Applications”, andapplication Ser. No. 11/973,260, Filed Oct. 5, 2007 for “Modular TaperedHollow Reamer For Medical Applications”, the disclosures of which arehereby incorporated in their entirety by reference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a modular easy-to-assemble taperedhollow reamer for medical applications; and more particularly, to ahollow tapered reamer having a disposable reamer assembly, which can beattached to a reusable shaft portion and includes a bone debriscapturing cavity.

2. Description of the Prior Art

Reaming of the internal canal of bones is required in many surgicalprocedures of orthopedic surgery. These procedures include hipreplacement, knee replacement and shoulder replacement. Reamers are alsoused in procedures that involve the internal fixation of fractures.Prior art reamers typically fall into two major classes: rigid andflexible shaft. Typically, reaming of the internal bone canal isachieved through utilization of a solid cylindrical or tapered reamer.Solid cylindrical or tapered reamers currently utilized are required tocut both cancellous bone (spongy bone) and cortical bone (hard bone).Cortical bone is generally denser and stronger, requiring an efficientcutter to machine the canal for a proper fit of the implant.Conventional reamers can cut cortical bone initially but can quicklydull after a single use, or at best a few uses. Once the reamer has dullcutting edges, it reduces the efficiency of bone cutting and in additiongenerates sufficient friction/heat to damage or kill the surroundingbone. These prior art solid cylindrical or tapered reamers are intendedfor multiple uses and therefore become less efficient after eachsurgery, resulting in poor cutting performance and bone necrosis. Thesedull blades also incorporate bone debris or bone cement debris into theliving bone tissue, creating bone healing problems.

U.S. Pat. No. 4,116,200 to Braun et al. discloses a milling tool forsurgical purposes. The surgical milling tool is a hand-operated millingmachine for milling the heads or sockets of bone joints and has aspherical shape. The tool is formed of a hemispherical cup integrallyformed with a cylindrical skirt and flange and is provided with aplurality of openings of semi-oval shape, each having a cutting edgearranged at the minor axis of the oval shape. The openings are situatedsuch that, upon rotation of the cup, the cutting edges thereof overlapto provide a continuous cutting edge surface conforming generally to theshape of the cup. The hemispherical shape of the cup provides theability to hollow out the arcuate shape of the bone joints. Bone andcartilage shavings are formed during the milling process and arecollected in a border area inside of the hemispherical cup. The surgicalmilling tool is provided for multiple uses and therefore the tool willbecome less efficient after each surgery, resulting in poor cuttingperformance and bone necrosis. Moreover, the spherically shaped reamingtool is not tapered.

U.S. Pat. No. 5,190,548 to Davis discloses surgical reamer. Thissurgical bone reamer includes a rotatable, elongated shank having aproximal end, a distal end and a longitudinal axis. A reaming headmounted on the distal end. A plurality of equally spaced walls isradially disposed on the reaming head around the longitudinal axis. Tipedges for penetrating bone are defined on the radial walls to bedisposed angularly with the longitudinal axis. Reaming edges joined tothe tip edges extend longitudinally from the tip edges in the proximaldirection parallel to and an equal radial distance from the longitudinalaxis for reaming a cylindrical tunnel when the reaming head is rotatedin bone. Tapered flutes disposed angularly between the tip edges and theradial walls permit bone to be evacuated through the reaming head whenforming a tunnel in bone. The reaming head is provided with angular tipsand edges for penetrating the bone and is thus not a single usedisposable cutter. The debris created is not stored away from thecutting edge and thus previously cut material may be included in thebone.

U.S. Pat. No. 5,549,613 to Goble et al. discloses a modular surgicaldrill. This modular surgical drill is in the form of a rigid drill shaftand a drill bit, which are connected together by a tongue-and-groovearrangement attaching the rear end of the drill bit to the forward endof the drill shaft. Each of the shaft and drill bit are provided withthrough bores extending centrally through their entire length. Thesebores become aligned upon assembly of the drill bit and shaft. Themodular drill is intended to be employed with a guidewire for drillingholes into bone. The assembled drill bit and shaft are placed on theguidewire and moved down such guidewire into contact with the bone,whereupon a tunnel may be formed into the bone by rotating and advancingthe drill bit along the guidewire. The dimensions of the bore andguidewire are so selected as to prevent the drill bit and drill shaftfrom moving relative to one another once they are assembled and mountedon the guidewire. Debris created during drilling is not removed andcollected away from the cutting location. The central bore is solid andas such does not receive cut bone debris. The cutter used is notdisposable.

U.S. Pat. No. 5,556,399 to Huebner discloses a bone-harvesting drillapparatus and method for its use. A coring drill harvests bone from adonor area of the human body. The drill bit is formed with acylindrical, hollow shaft and a half-conical tip or cutting head. Thecutting head is provided with a sharpened edge, which meets at an apexwith a non-sharpened edge, forming an obtuse angle of approximately 120degrees. The sharpened edge is configured to cut into bone when thedrill bit is rotated in a clockwise direction. With the apex directedagainst a section of bone, the cutting edge sheers off fragments ofbone, which are then drawn upwardly through the hollow shank of thedrill bit. As the drill bit is forced downwardly, continuous cuttingaction occurs and the morselized bone can then be removed from the shankand used to build-up bone in other areas to which it is transplanted.The drill bit fittingly mates on the distal end a fitting that rendersthe drill bit physically compatible with a conventional chuck. The bitincludes a pair of diametrically opposed, oppositely inclined recessesthat cooperate with a crossbar member within a bit-receiving bore of thefitting. When the aligned drill bit is pressed into the fitting, thecrossbar member cams along the inclined recesses causing the bit torotate relative to the fitting. The resulting frictional engagementbetween the recesses and the crossbar member, along with a detentassembly between the bit and the fitting, securely lock the bit onto thedistal end of the fitting, yet render removal possible by the use of aremoval tool. The bone harvesting tool provides a non-disposable cutter.Reuse of the cutter dulls the beveled lip edges. Moreover, the harvestedbone collection central bore requires a thorough cleaning prior to eachuse, creating contamination possibilities.

U.S. Pat. No. 5,690,634 to Muller et al. discloses a medullary drillhead. This drill head for intramedullary drilling has a front part, amiddle part and a rear part and is shaped as a hollow body ofrevolution. The front and rear parts have spiral slots formed withcutting edges. The rear part has an attachment for coupling to adrilling shaft. The drill head is not disposable, and as a result, thedrill head is continuously reused, resulting in dulling of the cuttingedges. Moreover, the drill head includes three openings in the form ofspirally shaped slots configured to have cutting edges similar to agrater; and has no place to collect bone debris.

U.S. Pat. No. 5,954,671 to O'Neill discloses a bone harvesting methodand apparatus. This apparatus and method harvests bone using a manual,cylindrical, multi-directional coring device with a guided deliverysystem that can be inserted through a percutaneous or closed approach toextract precisely measured amounts of bone or bone marrow. A series ofguide wires, obturators, dilators and cannulas are used as the exposureand delivery instrumentation for a cutting tool. The cutting tool has atip with six cutting edges for cutting in all directions. This apparatusis a manual, cylindrical, multi-directional coring device with a guideddelivery system to extract precisely measured amounts of bone or bonemarrow. The cutter portion of the device is not disposable and issubject to wear and dull edges. This coring device does not suggest atapered reamer.

U.S. Pat. No. 5,976,144 to Fishbein et al. discloses a hollow domereamer with removable teeth. This surgical reamer has a hollow dome withapertures spaced apart arranged in arcs extending from an apex of thedome to the base portion of the dome, and removable teeth positioned inthe apertures. Each cutting tooth has (i) a flange that is aligned flushwith the external surface of the dome, (ii) a raised cutting edgeextending above the flange and the external surface of the dome, and(iii) an interior passageway communicating between the outside andinside of the dome. A base plate may be removably secured on the baseportion of the dome to provide closure for the central cavity of thedome. Although the teeth are removable, they are not disposable innature; the teeth are removed for replacement or for re-sharpening andare used again. Removal of the small teeth may be cumbersome anddifficult, and may even pose a danger during removal as the personremoving the teeth may be cut by the sharp edges; replacement of theteeth into the apertures of the reamer will likely pose the sameproblems. The bone debris is not collected away from the cutting edgesof the teeth. This hollow domed reamer is spherically shaped reamer;does not suggest a tapered reamer.

U.S. Pat. No. 5,980,170 to Salyer discloses a tool driver. This tooldriver has a shaft with a longitudinal axis and opposite ends. A boss issecured at one of the shaft ends by which the tool driver is connectedto a rotary tool. A tool collate is secured at the other of the shaftends by which the tool driver may be driven by a surgical hand piecehaving a chuck in which the collate may be positioned. The boss has adistal end surface with a groove therein. Both the groove and the distalend surface extend transversely of the axis. A pin is positioned in thegroove on the axis. A latch mechanism is provided to hold a mounting barof a rotary tool in the groove on the pin, whereby the rotary tool isheld exactly coaxially of the driver during use. The rotary tool, whichis used with the driver has a bar containing the same dimensions as thegroove in the boss of the tool driver. The bar thus fills and iscomplementary to the slot. The bar has a hole therein which iscomplementary to the pin. The pin extends coaxially of the shaft and theboss. The bar hole in which the pin of the tool driver is positioned isprecisely coaxial of the axis of the tool about which the cutting edgesare precisely positioned. The cutters are connected to the tip of theshaft and are spherical in nature for joint and patella reaming. Inaddition, the reamer cups are not disposable in nature. The bonefragments are not collected and kept away from the cutting edge. Thisspherically shaped reamer is not tapered.

U.S. Pat. No. 6,193,722 to Zech et al. discloses a hollow milling tool.The hollow milling tool produces substantially hollow cylindricaldepressions in human or animal tissue. It also produces tissue pillars,which are removed at a harvest location, transported to a defectlocation and implanted. The hollow milling tool has teeth for theablation of tissue which are arranged at the distal end of the millingtool at the end side. Furthermore, the milling tool has passages fortransporting a cooling fluid to a cooling region of the milling toollying near the distal end during the ablation of tissue. Teeth areconstructed within the milling tool for accomplishing the depressions.These teeth will eventually need sharpening as the tool is used overtime. No structure is contained within the '722 patent that discloses orsuggests a tapered reamer.

U.S. Pat. No. 6,332,886 to Green et al. discloses a surgical reamer andmethod of using same. This device is used for expedited reaming of amedullary canal. The device includes a reamer head connected at thedistal end of a rotatable drive shaft. The reamer head has a cuttinghead with five blades and flutes therebetween. Each blade has a frontcutting portion. The blades can also include a side cutting portion. Themethod for removing material from the medullary canal of a bone includesthe steps of reaming an area of the medullary canal to remove material;irrigating the material to be removed while reaming to reduce generationof heat and move removed material from the reaming area; and aspiratingthe removed material while reaming to create a negative intramedullarycanal pressure to assist in the removal of the material. The blades andflutes at the reamer are reused and are subject to dulling. The bonechips are to be removed by the irrigating fluid, which means they arealways present adjacent to the cutting portions and may be forced intothe bone tissue. No disclosure in the '886 patent suggests a taperedreamer.

U.S. Pat. No. 6,451,023 to Salazar et al. discloses a guide bushing forcoring reamer, storage package for reamer assembly, and method of use.This guide bushing for a coring reamer has a tapered member with itslargest diameter at its first end so that the guide bushing frictionallyengages an internal surface of the reamer with a line contact. The guidebushing has a passage sized to slidably receive a guide pin. In use, thebushing advances in the proximal direction within the coring reameralong a guide pin while the excavated bone enters the passageway throughthe reamer. A storage package specifically designed for the reamerassembly is employed to remove the excavated bone from within thereamer. The package has a closed distal end and an open proximal endcloseable with a cap. With the coring reamer received in cantileveredfashion through a central opening of the cap of the tube, and with anadapter that couples the coring reamer to a handpiece installed, awrench is placed over the adapter and turned while the user gripsperipheral surfaces of the cap to prevent rotation of the coring reamer.A plunger is inserted through the opening and through the coring reamerfrom the proximal end. The plunger is pushed through the reamer untilthe bone core and bushing fall out of the distal end of the coringreamer. The guide bushing for a coring reamer is appointed with an openend surrounded by peripheral teeth. The teeth are arranged peripheral tothe body of the tube of the reamer. The tube is hollow and thereforeexcavated bone accumulates therewithin. The reamer, bushing andpackaging are disposed of after use. The '023 patent discloses a boneexcavating tool that does not prepare bone canal for implantation offemoral implants. No structure is disclosed therein that suggests atapered reamer.

U.S. Pat. No. 7,074,224 to Daniels et al. discloses a modular taperedreamer for bone preparation and associated method. This kit is for usein performing joint arthroplasty and includes a trial and a reamer. Thereamer is said to be useful when preparing a cavity in theintramedullary canal of a long bone with the use of a driver, and toassist in performing a trial reduction. The reamer includes a firstportion for placement at least partially in the cavity of the long boneand a second portion operably connected to the first portion. The reameris removably connected to the driver to rotate the reamer. The trial isremovably attachable to the reamer. This tapered reamer is notdisposable and does not have provision for accumulating bone debris awayfrom the cutting portion of the bone.

U.S. Patent Application Publication No. 2005/0113836 to Lozier et al.discloses an expandable reamer. This expandable reamer includes acannulated shaft and a plurality of straight cutting blades havingdeformable points. The blades are hingably outwardly rotatable at thedeformation points between a contracted position and an expandedposition. In the contracted position, the blades are substantiallyparallel to the longitudinal axis of the cannulated shaft and, in theexpanded position, the blades have at least a portion oriented radiallyoutward from the longitudinal axis, thereby forming a larger diametercutting surface in the expanded position and in the contracted position.The blades are formed from a portion of the cannulated shaft by, e.g.milling longitudinally extending slots through the wall of thecannulated shaft. The slots serve as flutes dividing the cutting edgeand trailing edge of each adjacent blade. Each blade may also includemore than one segment arranged along its length, the segments beingcoupled by deformation points. The expandable reamer may be used forcutting a cavity in a bone or other structure that is larger than thediameter of the entry point into the bone and greater than the diameterof the contracted reamer. The expandable reamer is not disposable. Sincethe expandable blades are deformably attached to the cannulated shaft,the cut bone debris is not collected away from the bone cutting region.As a result, fragments of cut bone debris may be pushed into the bonetissue by the deformable rotating blades.

U.S. Patent Application Publication No. 2006/0004371 to Williams et al.discloses an orthopedic reamer. This orthopedic reamer is for use increating and sizing canals in a bone. The orthopedic reamer includes anon-polymeric cutting portion having at least one cutting surfacethereon and a polymeric body portion covering at least a portion of thecutting portion. The at least one cutting surface is not covered by thepolymeric body portion. The orthopedic reamer provides cuttingcomponents including a blade or saw like construction, rather than theplurality of teeth. Although the orthopedic reamer is appointed fordisposability, the publication requires that the entire reamer, and notjust the cutting portion, be disposed of. That is to say, the entirereamer, including the non-polymeric cutting portion and the polymericbody portion of the device are all disposed of; not just the cutter.

There remains a need in the art for a modular easy-to-assemble hollowtapered reamer for medical applications having a disposable hollowcutter assembly. Also needed in the art is a disposable hollow cutterassembly of the type described, which can be attached to a reusableshaft portion that provides means for reaming of the internal canal ofbones. Further needed in the art is a cutter assembly having means forcollecting bone debris and keeping the collected debris displaced fromthe cutting edges, so that after one use of the reamer a new hollowcutter assembly can be utilized and the old hollow cutter assembly canbe discarded.

SUMMARY OF THE INVENTION

The present invention provides a modular easy-to-assemble hollow taperedreamer for medical applications having a disposable cutter assembly. Thecutter sleeve is attached to a reusable shaft portion of the reamer andhas a space for bone debris collection, which prevents inclusion of boneand bone cement debris into the living bone tissue. The reusable shaftportion has an integral or user attachable conical section containingone or more slots that receive the disposable cutter and therebytransfer shaft torque to the cutter. The reusable shaft is threaded atthe distal end to secure the tapered hollow disposable cutter sleeve,while the proximal end has coupling features for attachment with a drillor other machinery providing rotational torque. The portion of the shaftbetween the conical section and the proximal end with the coupling maybe rigid or flexible. A flexible shaft permits reaming of bone tissuethat is not directly in line and therefore not easily accessible with astraight shaft. A threaded modular pilot is provided with a collet thatmates with the tapered hollow disposable reamer, thereby producingsubstantial coincidence of alignment between the centerline of thereamer sleeve with that of the reusable shaft. Preferably, a freshtapered hollow reamer sleeve is used with each new application.Alternatively, the tapered hollow reamer sleeve is used several timesand, after it has become worn or dull, is discarded. The tapered hollowreamer includes a plurality of apertures and is hollow to allow spacebetween the reamer and the reusable shaft for bone and bone cementdebris collection. The tapered hollow reamer sleeve is supplied indifferent sizes, wherein the distal end dimension D1 is smaller thanthat of the proximal end. With this arrangement, there is produced areamer especially well suited for reaming a tapered hollow cavity. Thesemi-cone angle of the reamer may range from about 0.5 degrees to 5degrees and is determined by the equation.

$\alpha = {\frac{180}{\pi}\; \arctan \frac{\left( {{D\; 2} - {D\; 1}} \right)}{L}}$

wherein α=semi-cone angle in degrees;

-   -   D1 is the distal diameter of the tapered hollow reamer sleeve;    -   D2 is the proximal diameter of the tapered hollow reamer sleeve;        and    -   L is the length of the tapered hollow reamer sleeve;

Thus, the semi-cone angle depends on the length of the tapered hollowreamer sleeve and the diameters of the distal and proximal ends. Atapered hollow reamer reusable shaft, and a tapered hollow reamer sleeveof a selected length and modular pilot are provided as a matching set,while the reusable shaft and modular pilot may be used with one sleeve,or with matching tapered hollow modular sleeves.

The preferred semi-cone angle is 2 degrees and this is the case when thedistal end dimension is 2 mm smaller than that of the proximal enddimension and the tapered hollow reamer sleeve has a length of 57 mm.The reamer sleeves are provided in a plurality of sizes with distal enddimension ranging from 7 mm to 18 mm, in step increments of 1 mm. Thusthe semi-taper angle of the reamed bone conical cavity is exactly 2degrees for each of these reamers, which ream a bone cavity tosubstantially the same depth of up to 57 mm and produce a bone cavitywith substantially the same semi-cone angle of 2 degrees. Each reamer isattached to a shaft using a modular pilot with a threaded connection.When the modular pilot is tightened at the threaded end of the reusableshaft, the tapered collet of the modular pilot bears against the taperprovided in the tapered hollow reamer, thereby causing substantiallycoincident alignment between the centerline of the reamer and that ofthe reusable shaft. There are 4 shaft sets provided. Each shaft isdesigned to engage with two or three tapered hollow reamer sleeve sizes.For example, a shaft marked 9-10-11 engages with a 7 mm×9 mm reamer, an8 mm×10 mm reamer and a 9 mm×11 mm reamer. The reamer portion isprevented from free rotation by one or more slots in the shaft coneelement and tabs in the tapered hollow reamer. Torque from the shaft istransferred to the reamer, providing bone cutting action. Thus when adrill or other hand machinery rotates the reusable shaft, the shafttorque is transferred to the reamer through the tabs while the reamer isheld securely at the centerline of the rotating reusable shiftpreventing any wobbly motion. This disposable sharp hollow reamertherefore reduces heat generated during cutting by removing the bonedebris from the outer surface of the reamer to the inside of the reamer,while the bone debris collected may be used later for bone grafting andother specific surgical procedures. A further advantage of the hollowdesign is that by allowing the removal of the bone debris from the outersurface of the reamer to the inside of the cutter, the reamer is lesslikely to raise the intramedulary pressure in the long bone beingreamed, thereby lessening the chance of fat embolism during theseprocedures. Also fragments of bone chips or bone cement are notincorporated in the living bone tissue by the reamer cutting action.

During assembly, the tapered hollow reamer sleeve is captured betweenthe conical element of the shaft's central section and the conicalportion of the modular pilot as the shaft's distal ends thread engagewith the threads provided in the modular pilot. In a first embodiment,the shaft has male threads at the distal end and the modular pilot has afemale threaded central aperture, and the length of the shaft projectingbeyond the central conical section is slightly greater than the lengthof the tapered hollow reamer sleeve. In a variant of the firstembodiment, the length of the shaft extending from the central conicalsection is less than the length of the tapered hollow reamer sleeve, andthe modular pilot with the central threaded aperture is extended so asto provide an engaged length slightly exceeding the length of thetapered hollow reamer sleeve. In a second embodiment the threadedengagement of the distal end of the shaft with that of the modular pilotis made possible by having female threaded aperture on the distal end ofthe shaft, engaging with a male threaded pin centrally extending fromthe modular pilot. The length of the shaft may be slightly greater thanthat of the length of the tapered hollow reamer sleeve. On the otherhand, the length of the shaft may be smaller than the length of thetapered hollow reamer sleeve and the extension of the male threaded pinfrom the modular pilot is sufficiently long to provide an engaged lengththat is slightly greater than the length of the tapered hollow reamersleeve.

Generally stated, the reamer for medical applications comprises: (a) areamer reusable shaft having an elongated body with a proximal end, aconical central element and a distal end, said proximal end having acoupling portion appointed for attachment of said reamer to a drillingdevice, said distal end having a threaded portion; (b) said centralportion of said reamer reusable shaft having a pre-assembled coneelement or a modular user assembled cone element having two or morelateral slots; (c) a disposable tapered hollow reamer comprising: (1) adisposable hollow reamer sleeve portion having an outer surface, saiddisposable hollow reamer sleeve portion further comprising a pluralityof cutting teeth and a plurality of apertures on said outer surface; andat least one torque transmitting tab integrally attached to said hollowcutter sleeve at a larger diameter end designed to engage with at leastone slot of said shaft conical central element, thereby transferringtorque from said reusable shaft to said hollow tapered reamer sleeve;(3) the smaller diameter end of the tapered hollow cutter sleeve havinga collet taper; (d) a modular pilot with an external collet taper thatengages said collet taper of said hollow tapered reamer sleeve and afemale threaded aperture for engaging with the shaft distal end threadsand centering said tapered hollow reamer sleeve during assembly.

The present invention of modular tapered reamer solves the problemsassociated with the prior art reamers. In accordance with the presentinvention, the modular tapered hollow reamer for medical applicationshas an easy-to-assemble disposable modular hollow tapered reamer sleeve,which can be attached to a reusable shaft that allows for a fresh cutterassembly to be used with each new application of the reamer. The modulartapered hollow reamer of the present invention transfers shaft torquereliably while at the same time maintains the centerline of the reamerpreventing wobbliness thereof during cutting. Bone and bone cementfragments are collected and stored away from the bone cutting areathereby reducing the possibility of bone fragment incorporation intoliving bone tissue. The modular tapered hollow reamer gradually cratesthe bone cavity due to the taper provided, thereby reducing heat duringits surgical usage. Owing to the presence of these features, the modulartapered hollow reamer of this invention is safer to use and operatesmore efficiently than prior art reamers.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be more fully understood and further advantages willbecome apparent when reference is had to the following detaileddescription of the preferred embodiments and the accompanying drawings,in which:

FIG. 1 is a perspective view depicting a medical tapered reamer found inthe prior art;

FIG. 2 is a perspective view depicting an easy-to-assemble modularhollow tapered reamer in accordance with the invention;

FIG. 3 a is a cross sectional view of the easy-to-assemble modularhollow tapered reamer showing mechanical details in accordance with thefirst embodiment of the invention;

FIG. 3 b is a cross sectional view of the easy-to-assemble modularhollow tapered reamer showing mechanical details in accordance with thesecond embodiment of the invention;

FIG. 4 depicts two views, FIG. 4 a and FIG. 4 b of the disposable hollowtapered reamer sleeve;

FIG. 5 a illustrates a family of disposable tapered hollow sleevesincorporating the elements of the present invention;

FIG. 5 b illustrates a family of disposable tapered hollow sleeves, eachof which has a length of 57 mm in accordance with the present invention;

FIG. 6 a depicts a combination of multiple disposable tapered hollowsleeves attached to a single shaft;

FIG. 6 b depicts a combination of equal length multiple disposabletapered hollow sleeves attached to a single shaft;

FIG. 7 a provides an assembly view depicting the tapered hollow reamerassembly according to the first embodiment;

FIG. 7 n provides an assembly view depicting the tapered hollow reamerassembly according to the second embodiment; and

FIG. 8 depicts a mode of construction for the tapered hollow reamerassembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reaming of the internal canal of bones is required during manyorthopedic surgical procedures. These procedures include hipreplacement, knee replacement and shoulder replacement. Other surgicalprocedures that see the use of reamers include internal fixationprocedures for fractures. Typically, reaming of the internal bone canalis achieved through utilization of a solid cylindrical or taperedreamer, illustrated in FIG. 1. Prior art reamers typically include adriver coupling 11 (shown as a Jacob chuck connector), a sizedesignation 12, a pilot tip 13, a shaft 14, and cutting flutes 15. FIG.1 shows a tapered reamer, however cylindrical reamers of similar designalso exist in the prior art. Those solid cylindrical or tapered reamerscurrently utilized are required to cut both cancellous bone (spongybone) and cortical bone (hard bone). Cortical bone is generally denserand stronger, requiring an efficient cutter to machine the canal for aproper fit of the implant. Conventional reamers can cut cortical boneinitially but can quickly dull after a single use, or at best a fewuses. Once the reamer has dull cutting edges, it reduces the efficiencyof bone cutting and in addition generates sufficient friction/heat todamage or kill the surrounding bone. The bone or bone cement debriscollected is pushed against the living bone tissue and may beincorporated into the bone. Currently utilized solid cylindrical ortapered reamers are intended for multiple uses and therefore become lessefficient after each surgery, resulting in poor cutting performance andbone necrosis.

FIG. 2 depicts at 20 the modular disposable tapered hollow reamerassembly of the present invention, which provides the disposable hollowreamers appointed for use in medical applications. Due to its taper, itgradually enlarges the diameter of the bone canal reducing the amount ofpressure applied to the bone. A number of sizes of tapered hollowreamers are available along with their shafts and modular pilots so thatthe surgeon can choose progressively larger hollow tapered reamers for afresh bone canal or a reworked bone canal. Since the hollow reamersleeves are disposable, the cutting performance of the hollow reamer isnot compromised through repeated use. Several limitations of the priorart reamers and consequent clinical problems seen are overcome throughutilization of the disposable modular tapered hollow reamers herein.Novel design features of the hollow reamers of the present invention andimprovements to prior art reamers are multifaceted. The design includesa reusable shaft 23 with one or more lateral slots in a central conicalsection. A disposable tapered hollow reamer sleeve 26 is slid over thecentral conical section engaging torque transmitting tabs of the taperedhollow reamer sleeve with the slots. The disposable tapered hollowreamer is held in place by the modular pilot 27, which is screwed intothe threaded distal end of the shaft 23. During this threadedattachment, a collet taper of disposable tapered hollow reamer sleeve 26engages with a corresponding collet taper provided on the externalsurface of the modular pilot 27, substantially aligning the centerlineof the disposable tapered hollow reamer sleeve 26 with that of thereusable shaft 23. The end of modular pilot 27 that is distal from thecollet taper has a blunt or bullet shape, which facilitates centering ofthe tapered hollow reamer. The male thread of the shaft distal end andthe female central thread of the modular pilot may be provided with aleft-handed thread, so that the attachment does not come loose duringthe reaming operation. The shaft 23 is attached to a drill at 21. Anumber of shaft sizes can be selected from a kit and the shaft size isindicated at 22. The drill depth is indicated by depth markings 24.Shaft 23 has an integral or user attached cone section 25 and adisposable hollow reamer sleeve 26. The modular pilot may carry indiciarepresenting a shaft size to which it may be connected. Preferably, thehollow reamer sleeve 26 is discarded after a single use to ensure asharp cutter during surgery. Alternatively, the hollow reamer sleeve 26is used several times and after becoming worn is discarded. Varioustechniques may be used to determine if the hollow reamer sleeve is wornenough to require disposal. Such techniques may include measurements ofthe sharpness of the hollow reamer sleeve. Moreover, when dealing withrevision hip surgery, the hollow reamers have also been designed to cutbone cement (PMMA) in a more efficient manner by providing internalspace 34 to capture the debris. This feature reduces both the cuttingtemperature and time required to remove the remnant cement mantle. Thebone debris collected and removed may be used for bone grafting or otherspecific surgical procedures. A further advantage of the hollow designis that by allowing the removal of the bone debris from the outersurface of the reamer to the inside of the reamer, the reamer is lesslikely to raise the intramedulary pressure in the long bone beingreamed, thereby lessening the chance of fat embolism during theseprocedures.

FIG. 3 a depicts at 30 the mechanical attachment details of the modulardisposable tapered hollow reamer assembly according to the firstembodiment. Identical indicia are used to keep track of variouscomponents. The reusable shaft 23 has the shaft cone element 25 with oneor more slots 31, one above and one below are shown. The tapered hollowreamer sleeve 26 has two torque transmitting tabs 32 engaging into theslots 31 of the shaft cone element 25. As a result, when the shaft 23 isrotated, the tapered hollow reamer sleeve is also rotated with noslippage. The distal end of the tapered hollow reamer is provided with acollet taper as shown at 37. The distal end of the shaft 23 is threadedas shown at 35. A modular pilot 27 has female threads 36 that mate withthe shaft distal end threads. The modular pilot has a collet taper at 38that mates with the collet taper 37 of the tapered hollow reamer,centering the reamer as it is tightened. The space 34 that is betweentapered hollow reamer sleeve 26 and the reusable shaft 23 receives thebone and bone cement debris.

FIG. 3 b depicts at 30 the mechanical attachment details of the modulardisposable tapered hollow reamer assembly according to the secondembodiment. Identical indicia are used to keep track of variouscomponents. The reusable shaft 23 has the shaft cone element 25 with oneor more slots 31 (one above and one below are shown). The tapered hollowreamer sleeve 26 has two torque transmitting tabs 32 engaging into theslots 31 of the shaft cone element 25. As a result, when the shaft 23 isrotated, the tapered hollow reamer sleeve is also rotated with noslippage. The distal end of the tapered hollow reamer is provided with acollet taper as shown at 37. The distal end of the shaft 23 has femalethreads as shown at 35. A modular pilot 27 has male threads 36 that matewith the shaft distal end threads. The modular pilot has a collet taperat 38 that mates with the collet taper 37 of the tapered hollow reamer,centering the reamer as it is tightened. The space 34 that is betweentapered hollow reamer sleeve 26 and the reusable shaft 23 receives thebone and bone cement debris.

FIG. 4 illustrates in two views the design of the tapered hollow reamersleeve. FIG. 4A is a front view depicting the disposable hollow reamerwhich has one or more torque transmitting tabs (two shown in thedrawing) on the larger diameter end and a collet taper in the smallerdiameter end. FIG. 4 b shows a perspective view of the larger diameterend with two torque transmitting tabs. FIGS. 4A and 4B depict at 26 thedisposable hollow reamer sleeve, which comprises: (i) a disposablehollow reamer sleeve portion having an outer surface 41 having a hollowconstruction, the disposable hollow reamer sleeve portion furthercomprising a plurality of cutting teeth 42 and a plurality of apertures(also at 42) on the outer surface 41; (ii) a plurality (two shown) oftorque transmitting tabs 43 integrally attached to the tapered hollowreamer; at the larger diameter end and (iii) a collet taper 44 on thesmaller diameter end. Preferably, the cutting teeth 42 protrude from theouter surface of the disposable hollow cutter sleeve, consequentlyforming the plurality of apertures. Alternatively, the plurality ofapertures can be separate and distinct from the cutting teeth on theouter surface of the disposable hollow cutter sleeve.

The thickness of the hollow reamer sleeve portion should impartsufficient strength to withstand offset loads and axial loads on thereamer shaft during advancement of the cutter. The amount of load thatcan be tolerated without warping or changing the accuracy of themachined cavity can be determined by laboratory tests, which replicateclinical usage of the instrument. Typically, the disposable hollowreamer sleeve portion has a wall thickness ranging from 0.005 to 0.039inch. Preferably the wall thickness of the hollow reamer sleeve portionranges from 0.010 to 0.032 inch, and most preferably from 0.012 to 0.015inch. These thickness facilitate cutting by a disposable, low cost,hollow reamer sleeve in an accurate, efficient and reliable manner.

FIG. 5 a illustrates a family of disposable tapered hollow sleevesprovided. The family of disposable tapered hollow sleeves providedaccording to the present invention addresses a wide range of bone sizes,including sizes ranging from 7 mm through 18 mm in one (1) mmincrements; and being tapered and having a 7 mm tapering to a largerdiameter in one (1) to three (3) mm increments and having size optionsfrom a 7 mm base dimension to an 18 mm base dimension in one (1) mmincrements. The length of the reamer increases as the base size of thereamer is increased thereby having the ability to ream a deeper bonecavity.

FIG. 5 b illustrates a family of preferred equal length disposabletapered hollow sleeves. The family of disposable tapered hollow sleevesprovided according to the present invention addresses a wide range ofbone sizes, including sizes ranging from 7 mm through 18 mm in one (1)mm increments. Each hollow tapered reamer increases by exactly 2 mm fromthe distal end to proximal end and has a length of exactly 57 mm. Allthese reamers ream a bone cavity with a 2 degree semi-cone angle to anidentical depth of 57 mm. The larger the reamer size, the larger is thediameter of the conical bone cavity.

Multiple disposable tapered hollow sleeves can be attached to a singleshaft, as is illustrated in FIGS. 6 a and 6 b. Preferably, a singleshaft will attach to at least two or three different sizes of disposablehollow reamers. The tapered hollow reamers of FIG. 6 a have unequallengths, while the tapered hollow reamers of FIG. 6 b have equal lengthsof 57 mm. This provides for the ability to combine various sized shaftswith various sized disposable hollow reamers. These reusable reamershafts have a coupling on the proximal end and a threaded portion in thedistal end. The shaft portion between the proximal end and the centralportion may be made flexible to facilitate insertion of the taperedhollow reamer. Each reusable shaft has an integrally attached or userattachable modular cone element with one or more lateral slots forreceiving the torque transmitting tabs of the tapered hollow reamersleeve, as shown in FIG. 4B, and a threaded portion at the distal endfor retaining the modular pilot in accordance with the invention.

FIG. 7 a provides an assembly view depicting the tapered hollow reamerassembly according to the first embodiment. The assembled taped hollowreamer and the three component parts are shown. The hollow reamer sleeve26 is inserted over the cone section 31 of the reusable shaft 23 withthe torque transmitting tabs of the tapered hollow reamer sleeve 26positioned within the shaft cone section lateral slots. The modularpilot 27 with a female threaded aperture is screwed on to the end of thereusable shaft with a male threading, capturing the disposable taperedhollow reamer sleeve. The collet taper is provided at the end portion ofthe tapered hollow reamer sleeve, and the modular pilot substantiallyaligns the centerline of the tapered hollow reamer sleeve with thecenterline of the reusable shaft.

FIG. 7 n provides an assembly view depicting the tapered hollow reamerassembly according to the second embodiment. The assembled taped hollowreamer and the three component parts are shown. The hollow reamer sleeve26 is inserted over the cone section 31 of the reusable shaft 23 withthe torque transmitting tabs of the tapered hollow reamer sleeve 26positioned within lateral slots of the shaft cone section. The modularpilot 27 with the male threads is screwed onto the end of the reusableshaft with a female threaded aperture, capturing the disposable taperedhollow reamer sleeve. The collet taper is provided at the end portion ofthe tapered hollow reamer sleeve, and the modular pilot substantiallyaligns the centerline of the tapered hollow reamer sleeve with thecenterline of the reusable shaft.

FIG. 8 depicts a mode of construction for the tapered hollow reamerassembly. Since the reusable shaft 23 has a coupling suited forattachment to a drill at the proximal end, it may be placed in a vice orchuck 81 to secure the reusable shaft in a vertical position, as shown.Next the tapered hollow reamer sleeve 26 is inserted over the shaft asshown, engaging the torque transmitting tabs of the tapered hollowreamer sleeve with the lateral slots provided at the cone section 31 ofthe reusable shaft 23. Next, the modular pilot is screwed into thethreads at the distal end of the reusable shaft 23 and is tightened witha wrench 83. The modular pilot may be provided with a set of notches toaccommodate a wrench. A handle 82 attached to the vice or chuck 81provides support during this tightening procedure.

Having thus described the invention in rather full detail, it will beunderstood that such detail need not be strictly adhered to, but thatadditional changes and modifications may suggest themselves to oneskilled in the art, all falling within the scope of the invention asdefined by the subjoined claims.

1. A reamer for medical applications, comprising: a. a shaft portionhaving an elongated body with a proximal end, a central conical elementand a distal end, said proximal end having a coupling portion appointedfor attachment of said reamer to a drilling device, said central conicalelement having one or more lateral slots said distal end having athreaded portion; b. a disposable tapered hollow reamer sleeve,comprising:
 1. a tapered hollow reamer sleeve having an outer surfaceand a hollow construction, said disposable hollow cutter sleeve portionfurther comprising a plurality of cutting teeth and a plurality ofapertures on said outer surface; and
 2. said tapered hollow reamersleeve having a larger diameter end with at least one integrallyattached torque transmitting tab;
 3. said tapered hollow reamer sleevehaving a smaller diameter end with a collet taper; c. a modular pilotwith a central threading and a external surface with a collet taper; d.said disposable tapered hollow reamer sleeve being adapted to slide oversaid distal end of said elongated shaft portion and said slots of saidcentral conical element with engaging torque transmitting tabs of saidtapered hollow reamer sleeve; and e. said modular pilot being insertedat a distal end of said shaft engaging threads and said collet taper onthe external surface engaging with said collet taper of said hollowreamer sleeve; whereby torque from the shaft is transferred to saidtapered hollow reamer with substantial coincidence of centerlines,preventing reamer wobbliness, and bone and bone cement debris iscollected in the space between the tapered hollow reamer and shaft.
 2. Areamer for medical applications as recited by claim 1, wherein saidshaft portion is reusable.
 3. A reamer for medical applications asrecited by claim 1, wherein said disposable tapered hollow reamer sleeveportion is easily assembled.
 4. A reamer for medical applications asrecited by claim 1, wherein said threaded portion of said distal end ofsaid shaft portion has a left-hand male thread for assembly into saidmodular pilot having a left handed female thread.
 5. A reamer formedical applications as recited by claim 1, wherein said threadedportion of said distal end of said shaft portion has a left-hand femalethread for assembly into said modular pilot having a left handed malethread.
 6. A reamer for medical applications as recited by claim 1,wherein said tapered hollow reamer sleeve has differently sized lengthsas a function of reamer size.
 7. A reamer for medical applications asrecited by claim 1, wherein said tapered hollow reamer sleeve has equallength regardless of the reamer size.
 8. A reamer for medicalapplications as recited by claim 1, wherein threaded engagement of thethreads of said shaft and threads of said modular pilot results in anoverall length sufficient to capture the tapered hollow reamer sleevebetween said conical element of the shaft and the collet taper of saidmodular pilot.
 9. A reamer for medical applications as recited by claim1, wherein said elongated body of said shaft portion further comprises aplurality of graduations to determine the depth of said disposablehollow cutter assembly in the canal of the bone during use.
 10. A reamerfor medical applications as recited by claim 1, wherein said elongatedbody of said shaft portion further comprises a marking to indicate itssize.
 11. A reamer for medical applications as recited by claim 1,wherein said modular pilot further comprises a marking to indicate itssize.
 12. A reamer for medical applications as recited by claim 1,wherein said modular pilot includes a flat portion being appointed forinsertion with a wrench.
 13. A reamer for medical applications asrecited by claim 1, wherein said disposable hollow cutter sleeve portionis appointed for a single, one-time use.
 14. A reamer for medicalapplications as recited by claim 1, wherein said disposable hollowtapered reamer sleeve is appointed for more than a single use dependingon the amount of damage to said reamer sleeve portion after its initialuse.
 15. A reamer for medical applications as recited by claim 1,wherein said shaft portion is solid.
 16. A reamer for medicalapplications as recited by claim 1, wherein said shaft portion is rigid.17. A reamer for medical applications as recited by claim 1, whereinsaid coupling portion of the shaft is attached to a drilling machineusing a rigid shaft.
 18. A reamer for medical applications as recited byclaim 1, wherein said coupling portion of the shaft is attached to adrilling machine using a flexible shaft.
 19. A reamer for medicalapplications as recited by claim 1, wherein said tapered hollow reamersleeve has a wall thickness ranging from 0.005 to 0.039 inch.
 20. Areamer for medical applications as recited by claim 13, wherein saidsleeve has a wall thickness ranging from 0.010 to 0.032.
 21. A reamerfor medical applications as recited by claim 14, wherein said sleeve hasa wall thickness ranging from 0.012 to 0.015.